High speed rotary hook



Sept- 26, 1967 J. G. ATTwooD ETAL 3,343,510

HIGH SPEED ROTARY HOOK Filed Oct. 29, 1964 3 Sheets-Sheet 1 Sept' 26,l967 J. G. ATTwooD ETAL 3,343,510

HIGH SPEED `ROTARY HOOK 5 Sheets-Sheet 2 Filed Oct. 29, 1964 Sept. 26,1967 J. G. ATTwooD ETAL 3,343,510

HIGH SPEED ROTARY HOOK 3 Sheets-Shea?I 5 Filed Oct.. 29, 1964 'III V NsUnited States hatent 3,343,510 HiGH SPEED ROTARY HOOK .lohn G. Attwood,Oak Park, and Bernard F. Bishop, Chicago, iii., assignors to UnionSpecial Machine Company, Chicago, lll., a corporation of Illinois FiledOct. 29, 1964, Ser. No. 407,483 14 Claims. (Cl. 112- 228) ABSTRACT '0FTHE DISCLOSURE A rotary hook, for use in a lockstitch sewing machine,which includes a rotary component secured to a drive shaft of themachine and a bobbin case holder disposed within the rotary component,rotation of said bobbin case with the rotary component being prevented'by a stationary retaining finger carried by the frame of the machineand adapted to cooperate with the holder to prevent its rotation. Animportant feature of the construction is the provision of a race'way inthe rotary component that is adapted to receive a radially extending ribon the bobbin case holder, said raceway being disposed eccentrically inrela-tion to thc axis of rotation of the rotary component. Theeccentricity of the raceway is such that the point thereon which isdisposed at the greatest distance from the axis of rotation -to therotary component is so located that forces created upon high speedrotation of the rotary component are of such a character as to impart aminimum orbital movement to the bobbin case holder within the rotarycomponent. Toward the foregoing end, the region of the raceway which isat a maximum distance from the axis of rotation of the rotary componentis located at an angle of between 20 and 70 forwardly of a radial lineextending from the end of the loop seizing beak of the rotary componentto the axis of rotation of the latter. The foregoing feature enables therotary component of the hook to be operated at especially high speeds,at least 14,000 rpm., without causing overheating or producing otherobjectionable results. Toward the same end the invention also providesspecial features for lightening the weight of the rotary component andthe bobbin case holder. This is, in part, achieved by the provision ofspecial grooves at spaced intervals around the circumference of the ribprovided on the bobbin case holder. The construction in general is suchthat a shoulder on the bobbin case, which cooperates with a retainingfinger, is urged against the latter with only a relatively small forceat any time, thus enabling the free passage of the branch of a loop ofthread between said shoulder and the retaining linger at the dcsircdtime. This result is further insured by the formation of the retainingfinger in such a way that the part thereof which cooperates with theshoulder on the bobbin case holder will yield readily as thread is drawnoutwardly between the shoulder and retaining finger.

This invention relates to high speed lockstitch machines of thecharacter employed in factories requiring the production of locltstitchseams in garments of a variety of dierent types. Heretofore there hasbeen a definite limit upon the speed of operation of machines intendedfor the production of such seams, due to the necessity of rotating thehook at twice the speed of production of the stitches. Thus machinesadapted to produce such stitches at the rate of 5000 per minute haverequired rotation of the hook at a rate of 10,000 per minute. This hasled to considerable difficulty, in view of the excessive temperature andwear of various parts resulting from efforts to attain a higher speed ofoperation.

In accordance with the present invention the hook assembly is soconstructed that the hook is capable of asfissia rice rotating ut 14,000or more revolutions per minute, with the production of at least 7000locksttchcs per minute. Toward this cnd va number of important featuresare incorporatcd in thc construction of and the control over theoperation of the hook. ln the operation of a rotary hook it has beenfound desirable, at a certain point in its operation, to provide aclearance for the passage of the needle thread between a surface on thethread supplying container within the rotating component of the hook anda stationary linger or shoulder which prevents rotation of saidcontainer or basket, so as to permit withdrawal of the loop of needlethread that is carried around said basket, without danger of severingsaid thread. ln vertical yaxis hook machines a finger or similar memberhas frequently been provided to engage the basket to shift it slightlyagainst the action of the frictional forces tending to rotate it alongwith the rotary component of the hook. But it has Ibeen foundimpracticable to provide such hooi; opening means in connection withhorizontal axis hooks. In the patent to Attwood No. 2,941,488 it hasbeen disclosed how to achieve the purposes of such a hook opening fingerby the provision of a certain ccccntricity bctween the raceway of therotary component of the hook, which cooperates with the rib on `thestationary' basket component, and the axis about which said rotarycomponent is rotated. While this has proved to be highly beneficial, ithas not achieved the high speed operation of the hook made possible bythe prescrit invention.

This invention involves a combination of features which jointlycontribute toward the desired end. ln the preferred embodiment of theinvention there are three important features which contribute toward theachievement of the YStated result. One of these is the provision ofeccentricity between the axis of the shaft which carries the rotarycomponent of the hook and the raceway of said rotary component in a newrelationship that serves to retain the thread basket or bobbin caseholder in a relatively centralized position within the rotatingcomponent. For this purpose it has been found desirable to provide themajor axis of such ecccntricity along a line that extends substantiallyin the opposite direction from thc axis of the shaft carrying the rotarycomponent than that employed in the construction of the Attwood patentabove mentioned. This construction is such that it does not pro videautomatic shifting of the bobbin case basket in a direction to offsetthe frictional forces that tend to turn the basket in the direction ofrotation of the rotary component of the hook, as is done in theconstruction disclosed in said Attwood patent. Instead it serves, incombination with thc other features to he mentioned, to retain thebasket in a substantially centralized position, i.e. with a minimumorbital movement having a .radius of not more than about .006 of an inchand preferably less, so as to minimize the force with which the rib onthe basket is urged against the circumfcrentially extending and sunrounding surface of the raceway provided in the rotary component. Theforce of engagement of the cooperating opposed surfaces of the rib andraceway is reduced to about one-tenth of that encountered in hooks ofthe type heretofore proposed, including that disclosed in said Attwoodpatent. This greatly reduces the wear on and temperature rise of thecooperating surfaces and the necessity of lubrication thereof. lt alsogreatly reduces the impact or shock and noise incident to the high speedoperation or hooks of previously suggested constructions.

A second feature of the invention, which contributes toward theforegoing end, is the provision of cut-away sections in the radiallyextending rib of the bobbin basket holder. The location of thesecut-away portions of the rib has been carefully determined in accordancewith the present invention, through the use of an oscilloscopepresentation of the points in a cycle of rotation of therotaryvcomponent of the hook at which the greatest amount of shock orimpact, with resultant noise, is produced in the course of rotation ofthe rotary component. It was found, in accordance with these tests, thathooks of currently used constructions would, upon starting up, produceexcessive impact and noise as the foremost end of the raceway, at thetrailing side of the gap provided in the same in the region of the beakof the hook, reaches the leading end of the-rib on the bobbin caseholder. However, the provision of a cut-away portion in the rib in aregion about 36 forward in the direction of rotation of the pointmentioned, coupled with the eccentricity of the raceway described above,was found to greatly reduce this noise and impact created upon therotation of-the rotary component of the hook. Further oscilloscopestudies indicate that noises created during the continued revolution ofthe new hook could be greatly reduced through the provision ofadditional cutaway portions in the bobbin case rib at further 36circumferential intervals of the same. The total circumferential lengthof the rib is only about 288, in View of the necessity of omitting abouta 72 angular portion thereof in the region in which the needle passesdownwardly into the path of the loop seizing 'beak of the hook in orderto permit free upward movement of the needle thread loop to completeformation of the stitch. The raceway in the rotary hook is also omittedto a similar but somewhat smaller extent. It is this gap in thecircumferential areas of the rib and raceway, with resultant freeshoulders that are brought into alignment upon each revolution of therotary component, that apparently produces the excessive impact andnoise, referred to above, in hooks of previously known constructions. Onthe other hand, the present invention serves to eliminate these noiseand impact producing tendencies in the desired high speed operation ofthe machine, and thus enables the hook to be rotated at 14,000 r.p.m.without encountering the useful difficulties.

While in achieving the foregoing purposes of the cutaway portions of therib their radial depth may -be varied to a certain extent, it has beenfound highly desirable to make them of the full radial extent of theri'b on the bobbin case holder. Also it has been found desirable to makesaid cut away portions with a substantial circumferential extent, aboutor more, and also to provide them with smooth inwardly sloping surfacesforming a substantially V-shaped configuration. These aspects of theinvention serve to reduce the weight of the bobbin case holder and alsoto overcome the danger of having the needle thread caught in the groovesformed by the cut away .portions ofthe rib. The reduction in the weightof the holder contributes toward minimizing the force with which thecircumferentially extending opposed surfaces of the rib and raceway areurged together upon any lateral shifting of the bobbin case holder as aresult of operation of the hook, and reduces the lubricationrequirements for these surfaces.

The location of the maximum eccentricity of the raceway, in accordancewith the present invention, is such that it does not produce the openingaction to permit free passage of the needle thread between the bobbincase holder retaining nger and the cooperating shoulde-r on said holder.But the overall construction is such that the force with which saidshoulder is urged against said finger is relatively small, as comparedwith hook structures now in use, such as that disclosed in the` abovementioned Attwood patent. In the latter construction, the

.average value of the indicated force has been found to be `betweenabout 2 and 4 ounces, depending upon the speed of operation of themachine, i.e. between 3000 and 600,0 rpm., and it goes as high as ouncesin the course of a cycle of rotation of the hook, when the machine isoperated at 6000 r.p.m. These figures contrast sharply with the averageforce or pressure of about 0.2 ounce and maximum or peak pressu-re of0.5 ounce created during the operation of the vhook of this invention.Moreover, the average and peak pressures developed by the latter remainsubstantially uniform as the speed of operation of the machine isincreased from 3000 to 7000 or more -r.p.m.

A third feature of the overall combination of the present invention isthe provision of a retainer for the bobbin case holder which is a thinat spring carried by the retainer for cooperation with the shoulder onthe bobbin case holder to prevent rotation of the latter with the rotarycomponent of the hook. This spring element is interposed between saidshoulder and a more rigid finger that enters the recess in the outerface of the bobbin case holder and it provides the means cooperatingwith theshoulder men tioncd. This enables the needle thread loop to bedrawn upwardly between the spring element and the specified shoulder,even though the cooperating surfaces remain engaged under a relativelysmall force at the time the thread loop-is so drawn upwardly. The springclement tiexes sufficiently readily -to permit this to be done with outdanger of breaking the thread, when the greatly reduced force discussedabove is brought about by the other features of the invention. Ifdesired, a thin piece of plastic or synthetic rubber may be providedbetween the spring element mentioned and the more rigid finger. Thisplastic or synthetic rubber strip acts as a shock absorber and keeps thethin spring element from vibrating.

Wtih the foregoing features of the yinvention in mind, a preferredembodiment of the overall construction will now be described in detail-by reference to the accompanying drawings in which:

FIG. 1 is an enlarged face view ofthe improved rotary hook construction,shown in relation to the path of the needle and illustrating thepositions of the needle thread and bobbin thread at a point in the cycleof operation of the machine at which the needle thread loop is about tobe carried upwardly and released from the hook structure;

FIG. 2 is an enlarged perspective view of the improved rotary hook,showing the rotary component and the cooperating threads at a slightlylater point in the cycle of operation ofthe machine; i

FIG. 3 is a similarly enlarged plan view of the hook structure and ofthe bobbin case holder retainer;

FIG. 4 is a detail plan view, on a slightly larger scale,

' of a portion of the bobbin case holder retainer member illustrated inFIG. 3;

FIG. 5 is an enlarged end view of the retainer member as seen from theleft in FIG. 4;

FIG. 6 is a view similar to FIG. 4 showing, on an enlarged scale, amodified finger construction on the retainer, incorporating the abovementioned thin piece of plastic or synthetic rubber between the thinspring member and the more rigid part of the retaining finger;

FIG. 7 is a rear view of the bobbin case holder, on a quiteenlargedscale, and shows the preferred form and angular disposition of thecut-away regions ot' the radially extending rib;

FIG. 8 is a face View of the rotary component of the hook, on a scalecomparable with the showing of the bobbin case holder in FIG. 7, andshows the disposition of the eccentricity of the raceway in the hook inrelation to the axis of the shaft which carries the rotary component;

FIG. 9 is an enlarged face view of the bobbin case holder;

FIG. 10 is a similarly enlarged plan view of the bobbin case holder; and

FIG. 11 is an enlarged side elevational view of said holder.

The preferred embodiment of the invention as disclosed herein isparticularly suited for use in connection with a lockstitch sewingmachine of the type disclosed in the 'patent to Covert No. 2,977,910,granted Apr. 4, 1961.

main drive shaft of the machine. Within the rotary component of the hookthere is mounted a bobbin case holder 12 adapted to retain a bobbin case13 of conventional form. As shown in FIG. 3 there is provided a retainermember 14 for preventing rotation of the bobbin case holder along withthe rotary component of the hook as a result of frictional drive forcescreated between these elements. Member 14 is secured to the under faceof the work supporting member of the base portion of the frame of themachine by means of bolts or screws 15. Toward its left end the element14 (FIG. 3) is provided with an inwardly and upwardly extending finger16 arranged to cooperate with a groove 17 in the upper portion of theface of lthe bobbin case holder. Adjacent the finger 16 there isprovided a similarly shaped thin spring nger 16a also cooperating withthe groove 17. This arrangement is such that in the rotation of therotary component of the hook, in a counterclockwise direction (FIG. l),the shoulder of the groove 17 to the right of the spring finger 16a isurged under a light pressure or force against the spring finger 16a.

As shown in FIG. 3, the bobbin case holder is provided with an opening1S through which the needle is reciprocated in the course of operationof the machine. This enables carrying the needle downwardly into thebobbin case holder beneath the loop seizing beak of the rotary componentof the hook. It will -be understood that as the needle rises it tends tothrow out a slight loop in the path of the beak. The bobbin case holderhas a forwardly and upwardly extending outer flange portion 19 (FIGS. 9and l0), this having in its upper region the groove 17 described above.The bobbin :case holder has a main body portion 20 of substantiallycylindrical form, adapted to tit into a cavity Within the rotarycomponent of the hook. Various parts of the bobbin case holder arecut-away to lighten the overall weight of the holder. Thus the base orinner end of the holder is formed by a diametrically extending part 21with cut-away portions at each side thereof. At the center of part 21there is suitably secured an outwardly extending pin or stud 22 arrangedto receive the central tubular portion of the bobbin case 13. Toward theouter end of the stud 22 there is provided a groove 22b, leaving thehead portion 22a of substantially the same diameter as the main body ofthe stud. This provides for locking the bobbin case within the holder bythe conventional operation of a lever 13a and a slide element 13bcarried by the `bobbin case, said slide element cooperating with acut-out portion 19a in the flange of the bobbin case holder to retainthe bobbin case against rotation within the holder.

Extending around the body portion 20 of the bobbin case holder is a rib23 adapted to cooperate with the raceway in the rotary component,indicated at 24 in FIG. 8. The rib 23, as shown in FIG. 7 is cut-awayover an arc of about 72 in its upper portion to enable the passage ofthe loop of needle thread as this is drawn upwardly after having beencarried around the bobbin case holder. At intervals of preferably about36 from the edge 23a of the rib there is provided a series of grooves23h having their outer ends extending over an arc of approximately andhaving a generally V-shaped configuration with smoothly rounded surfacesat their radially inner ends. While the grooves or cut-away portions 23hof the rib need not extend the full radial depth of the rib, theypreferably do so. Also the surface 23b (FIG. 10) of each groove isinclined at an angle of between and 30 to a radial line extending fromthe axis of the stud 22 to the outer edge of the adjacent segment of therib. The opposite surface 23h" of each groove is preferably inclined atan angle of about 45 in the opposite direction. This disposition of thetwo surfaces avoids any danger of having the thread loop caught in thegrooves, along with other advantages. Since FIG. 7 is a rear view of thebobbin case holder it will be appreciated that the edge 23a is about inalinement with the right hand edge of part 21 as Viewed in FIGS. 9 and10. The other edge 23e` (FIG. 7) of the 72 gap in the rib is to the leftof part 21 in FIG. 9. As has been explained above, the spacing of thecut-away portions 23b has been determined through oscilloscope studies,and they have been found to greatly reduce the impact and noise incidentto the rotation of the rotary component of the hook. Also they serve tolighten the weight of the bobbin case holder and to provide a smallerarea of contact between the rib and the cooperating raceway of therotary component. Moreover the particular location ofthe center ofeccentricity of the raceway of the rotary component of the hook, coupledwith the other features described, is such as to impart a minimum pathof orbital movement to the bobbin case holder during the rotation of therotary component of the hook.

Turning now to the construction of the rotary component of the hook,this is similar to conventional constructions heretofore employed withthe exception of a particular disposition of the eccentricity of itsraceway in relation to the hook beak. As best shown in FIGS. 1 and 2 therotary component has a loop seizing beak 26 which is carriedcounterclockwise upon rotation of the hook. The outer peripheral portionof the rotary component involves two segments 27 and 2S which aresecured by screws to the main body of the rotary component. The separateconstruction of these elements enables the assembly of the bobbin caseholder within the raceway of the rotary component, which is in partprovided by the element 27. Referring to FIG. 8, there is indicated thedisposition of the eccentricity of the raceway in relation to the axisof the hook shaft 11. This axis is indicated at 11a and the center ofthe raceway is indicated at 25a. It will be seen that the latter isdisposed along a line 25 extending radially from the axis 11a of thehook shaft and is disposed preferably at a distance of .0010 inch, toprovide that amount of eccentrieity between these axes in the particulardirection indicated. Line 2S is preferably disposed at an angle of about45 forwardly of the end of the hook beak 26, in the direction ofrotation of the latter, but such angle may be between 20 and 70.

Returning now to FIGS. l and 2, the element 28 of the rotary componentis provided with a forwardly extending spur 28a spaced radiallyoutwardly to a slight extent from the hook beak and forming a V-shapedrecess for the retention of the needle thread which is seized by thebeak. Segment 27 of the rotary component has a thread guiding projection27a forwardly of the beak 26 and spur 28a. This insures proper controlover the needle thread loop as the latter is released from the beak andis pulled upwardly in the tightening of the stitch that has been formed.It will be appreciated that as the needle 29 is reciprocated through anopening in the work supporting surface 30, and carried into the path ofthe hook beak 26, the latter is enabled to pick up the loop of theneedle thread 31 and carry this around thread 32 supplied from thebobbin within the bobbin case. The latter thread is passed outwardlyfrom the interior of the bobbin case to a spring retaining linger 33 andthen upwardly through an eyelet 33a to its point of incorporation in thework being stitched.

As the seized loop of the needle thread is carried around the hook bythe beak 26, the branch thereof extending from the work piece beingstitched, on support 30, is urged outwardly by the edge 23e of member 2Sof the rotary component so as to pass along the outer surface of thebobbin case and its holder. In FIG. l the loop is shown in the positionassumed after about a half revolution of the rotary component in whichthe beak has seized the thread. In FIG. 2 the needle thread loop isshown in the position assumed after about another revolution oftherotary component, at which time the loop is pulled away from the beak 26by the action of the usual take-up mechanism provided on the machine,and it is temporarily retained by the projection 27a of segment 27 ofthe rotary component. As the hook continues to rotate, the loop will berelease from the projection 27a and the take-up mechanism will draw theloop upwardly against the underside of the work. In doing this thebranch of the loop referred to above will be pulled upwardly between thespring finger 16a on the retainer 14 and the cooperating shoulder ofrecess 17 in the bobbin case holder. This can be readily done in view ofthe relatively light pressure with which said shoulder on the bobbincase holder is urged against the spring linger 16a, and it is furtherfacilitated by the ability of the latter to flex away from saidshoulder.

As has been previously indicated, it has been found desirable to inserta thin strip of rubber or yieldable plastic material between the rigidfinger 16 and the spring finger 16a of the retainer 14. This isindicated at 34 in FIG. 6. The provision of such yieldable materialserves to eliminate or minimize any vibrations that may be imparted tothe spring finger 16a as the thread loop is drawn upwardly between itand the shoulder on the bobbin case holder, and is then released fromthe slight gripping force of the spring finger. Layer 34 will yieldsuflciently to permit the slight flexing of spring finger 16a, but thelatter will be prevented from vibrating upon the release of the thread.Some vibration may also be imparted to the spring finger 16a, in theabsence of the layer 34, due to the unavoidable impact action createdupon starting up of the machine. Such impact action appears to be due tothe fact that a certain amount of clearance must be provided between therib and raceway of the hook assembly to reduce the frictional drag ofthe rotary component and the bobbin case holder and to provide space fora thin lubricant nlm. This clearance naturally causes the bobbin caseholder to settle by gravity, when the machine is at rest so that theholder is slightly off center in relation to the raceway. The presentinvention serves to bring the bobbin case holder rather quickly into asubstantially centralized position as the machine is started up, andserves to reduce the orbital path of movement of the holder to a minimumduring operation of the machine.

The combination of the several features of the present invention,including the extent and direction of eccentricity of the hook racewayin relation to the axis of the hook shaft 11, the lightening of theoverall weight of the bobbin case holder, the provision of periodicgrooves or cutaway regions in the rib 23 of the bobbin case holderaround its circumferential extent, the provision of the yielding finger16a on the retainer 14, and also the provision of the rubber or plasticinsert 34 between the iingers 16 and 16a of the retainer, all contributetoward increasing the permissible speed of operation of the machine,beyond anything previously attained, without producing objectionableimpact and noise and with the production of uniform stitches. A hookconstructed in accordance with the invention has been trial tested andfound capable of operation at exceptionally high speed for longcontinuous periods of time, without developing objectionable impact andnoise, without overheating of the hook, and with a minimum requirementof the lubrication of the cooperating surfaces of the rib and raceway ofthe hook assembly. In fact it was operated continuously at 14,000 r.p.m.for 14 hours, and during the last three hours of this test the supply oflubricant to the raceway was cut off. Throughout the test, noobjectionable impact and noise was developed and no overheating of thehook was created. Those conducting the test found the hook to be thesmoothest acting hook they had ever tested, even with its higher thanusual speed of operation. This is indicative of the low torquetransmitted to the bobbin case holder and the low lubricant requirementof the improved construction.

While the particular construction shown and described herein has beenfound exceptionally well suited to achieve the highly advantageousresults explained above, various departures from the precise form shownmay be made and still obtain at least some of the important advantagesof the invention. Thus, as indicated by the foregoing, certain definiteadvantages result from the particular point or line of maximumeccentricity of the raceway. While this should preferably be locatedalong the line 25 indicate-d in FIG. 8, it may deviate somewhat fromthat line to the extent of as much `as 25 in either direction. As forthe grooves or cut-away portions provided in the rib 23 of the bobbincase holder, those are most desirably of the form and in the locationdescribed, but both of these factors may be varied to some extent. Theymay, for example, be spaced at a somewhat different angular distanceapart and either or both their circumferential extent at their outermostregions and their radial depth may be varied to some extent, Theirradical depth, for example, need not be to the full radial dimension ofthe rib. However the full depth shown in the drawings contributes towardthe advantage of reducing the weight of the holder. Furthermore arelatively large length of the grooves in a circumferential directionserves to reduce the area of the surface of the rib cooperating with thecircumferentially extending surface of the raceway, thereby reducing thetorque or frictional force created upon the rotation of the rotarycomponent. This objective is also achieved to a certain extent by thechamfered or beveled edges shown on the outer circumferential surfacesof the projecting portions ofthe rib.

Important aspects of the invention are the maintenance of asubstantially uniform and low pressure of the shoulder on the bobbinbasket against the retaining finger, the provision of a resilient andreadily yieldable portion of the finger that cooperates with saidshoulder, and the generation of a minimum amount of heat from thefrictional cooperation of the rib with the raceway. The constructionshown serves to hold the temperature of the hook at a level comfortableto the hand.

What is claimed is:

1. In a lockstitch sewing machine having a driven shaft, a rotary hookhaving a rotary component secured to said shaft, said rotary componenthaving a loop seizing beak, a bobbin case holder within said rotarycomponent, a stationany retaining finger cooperating with said holder toprevent rotation thereof with said rotary component, said rotarycomponent having a substantially annular raceway therein and said bobbin4case holder having a radially extending rib cooperating with saidraceway, said raceway being disposed slightly eccentrically in relationto the axis about which said rotary component is rotated, the region ofsaid raceway which is at a maximum distance from the axis of rotation ofsaid rotary component being located within a one-quarter circumferentialarc extending forwardly of the hook beak and being so disposed as tomaintain said bobbin case holder with minimum orbital move-ment withinsaid rotary component.

2. In a lockstitch sewing machine as set forth in sclaim 1, a lineextending from the axis of rotation of said rotary component of the hookto said region of the raceway which is at a maximum distance from saidaxis of rotation extending at an angle of between 20 and 70 forwardly ofa radial line extending from the end of said beak to the axis ofrotation of said rotary component.

3. In a lockstitch sewing machine as set forth in claim 2, a threadcarrying needle reciprocable along a path substantially perpendicular tothe axis of rotation of said rotary component of the hook, said racewaybeing omitted in the region of said hook beak over an arc of at least 45and said rib of said bobbin case holder being omitted over an arc of atleast 60 in the region of the reciprocation of said needle, said rib onsaid bobbin case holder being grooved in successive areas disposed atsubstantially equal distances apart around the circumference of said ribfrom one end thereof to the opposite end thereof, said grooved areas ofsaid rib being provided with gently lsloping surfaces from the outerface of the rib toward the radially inward portions of said groovedareas and there being merged smoothly into each other to provide asubstantially V-shaped configuration.

4. In a lockstitch sewing machine as set forth in claim 3, the radialcenter lines f said grooves being disposed at about 36 intervals aroundthe circumference of said rib.

5. In a lockstitch sewing machine as set forth in claim 4, said groovedareas of said rib extending over an arc of about around the periphery ofsaid rib.

6. In a lockstitch sewing machine as set forth in claim 1, saidretaining finger having a portion thereof cooperating with a shoulder onsaid bobbin case holder, said portion of said finger being so formed andretained as to enable the same to yield slightly upon the application ofa relatively small lateral force thereto.

7. In a lockstitch sewing machine as set forth in claim 3, saidretaining finger having a portion thereof cooperating with a shoulder onsaid bobbin case holder, said portion of said finger being so formed andretained as to enable the same to yield slightly upon the application ofa relatively small lateral force thereto.

8. In a lockstitch sewing machine as set forth in claim 1, said bobbincase holder having a groove in the outer face thereof, said retainingfinger having a relatively rigid portion and a yieldable spring portionspaced slightly from said rigid portion both extending into said groove,said yieldable spring portion cooperating with a shoulder at one side ofsaid groove and being adapted to yield readily upon the passage ofthread from said needle between said shoulder and said spring portion.

9. In a lockstitch sewing machine as set forth in claim 8, a rubber likematerial filling the space between said rigid portion and said yieldablespring portion of said finger.

10. In a lockstitch sewing machine as set forth in `claim 1, said bobbincase holder having a shoulder that is urged against said retainingfinger upon operation of the hook, the extent and direction in which theaxis of said raceway is disposed away from the axis of rotation of saidrotary component being such as to create substantially the same lowpressure of the shoulder on the bobbin case holder against the retainingfinger during all speeds of operation of the machine above 3,000 r.p.m.

11. In a lockstitch sewing machine as set forth in claim 10, the rib onsaid bobbin case holder being provided with grooves in thecircumferential face thereof at spaced intervals, such groovessubstantially reducing the area of said circumferential face thatcooperates with the circumferential wall of said raceway in the rotarycomponent and thereby greatly reduces the torque applied to the bobbincase holder upon rotation of the rotary `component.

12. In a lockstitch sewing machine as set forth in claim 11, said areaof the circumferential face of the rib being reduced to such an extentthat the peak pressure of said shoulder against said finger is not morethan about 0.5 ounce during each revolution of the rotary component andthe average pressure is about 0.2 ounce.

13. In a lockstitch sewing machine as set forth in claim 1, thedisposition and amount of the eccentricity of said raceway in relationto the axis of rotation of said rotary component being such yas to causethe orbital movement of said bobbin case holder during al1 operations ofthe machine to be substantially cincular and have a radius or not morethan about .006 of an inch.

14. In a lockstitch sewing machine as set forth in claim 3, the surfacesat one side of each of said grooves provided in said rib which extendfrom the inner to the outer ends thereof being inclined at an anglebetween 20 and 30 to a line extending from the axis of rotation of saidrotary component to the outer ends of said surfaces, said inclinationbeing in the direction of approach of the loop seizing beak of saidrotary component, and the surfaces of said grooves lat the oppositesides thereof being inclined at a greater angle in the oppositedirection.

References Cited UNITED STATES PATENTS 1,364,279 1/ 1921 Hohmann 112-2282,108,412 2/1938 Sauer 112-228 2,232,624 2/1941 Nissen 112-181 X2,352,598 7/1944 Billington 112-181 X 2,941,488 6/1960 Attwood 112-2283,074,367 1/ 1963 Habedank et al 112-228 JORDAN FRANKLIN, PrimaryExaminer.

H. ROSS, Examiner.

1. IN A LOCKSTITCH SEWING MACHINE HAVING A DRIVEN SHAFT, A ROTARY HOOKHAVING A ROTARY COMPONENT SECURED TO SAID SHAFT, SAID ROTARY COMPONENTHAVING A LOOP SEIZING BEAK, A BOBBIN CASE HOLDER WITHIN SAID ROTARYCOMPONENT, A STATIONARY RETAINIG FINGER COOPERATING WITH SAID HOLDER TOPREVENT ROTATION THEREOF WITH SAID ROTARY COMPONENT, SAID ROTARYCOMPONENT HAVING A SUBSTANTIALLY ANNULAR RACEWAY THEREIN AND SAID BOBBINCASE HOLDER HAVING A RADIALLY EXTENDING RIB COOPERATING WITH SAIDRACEWAY, SAID RACEWAY BEING DISPOSED SLIGHTLY ECCENTRICALLY IN RELATIONTO THE AXIS ABOUT WHICH SAID ROTARY COMPONENT IS ROTATED, THE REGION OFSAID RACEWAY WHICH IS AT A MAXIMUM DISTANCE FROM THE AXIS OF ROTATION OFSAID ROTARY COMPONENT BEING LOCATED WITHIN A ONE-QUARTER CIRCUMFERENTIALARC EXTENDING FORWARDLY OF THE HOOK BEAK AND BEING SO DISPOSED AS TOMAINTAIN SAID BOBBIN CASE HOLDER WITH MINIMUM ORBITAL MOVEMENT WITHINSAID ROTARY COMPONENT.